Various shaft speed signal indicators have been heretofore proposed to develop voltages proportional to shaft speed. Such indicators are typically used to indicate failure of proper rotation or movement of a shaft or part of a machine such as a combine, for example, in which belt slippage or breakage or other malfunctions can cause considerable damage or loss of time if not immediately detected. Heretofore known shaft speed indicators have been comprised of a magnet secured to a collar adapted to rotate with a shaft and a reed switch which is responsive to the magnet moving therepast.
While such indicators were acceptable, there were numerous problems associated therewith. One of the problems involved with these heretofore known indicators involved setting a proper air gap between the reed switch and the magnets on the shaft. As will be appreciated, misadjustment of the air gap often resulted in damage to the component parts and/or inaccurate signals being developed by the sensor. The numerous parts comprising these known sensors also proved costly and burdensome in assembly.
Additional screws and related hardware were required for mounting the reed switch and magnets in their proper relation relative to each other. Moreover, the known sensors required a separate shield to guard or protect the free end of the shaft and the sensor against inadvertent damage. Such a shield required separate hardware for attaching the shield to a wall of the machine. Damage to the parts and the relatively delicate air gap adjustment for the indicator proves to be a continual problem when such speed indicators are used on agricultural equipment movable through a field and, thus, is subject to continual impact with corn stalks and other obstacles.
Thus, there is a need and a desire for a shaft speed signal indicator which mounts as a compact integral assembly to a shaft with a predetermined and proper air gap adjustment being maintained between the component parts and which shields the free end of the shaft.